Fig. 4.

GRO-binding sites of Six1a are required in vivo for the function of Six1a in the neuronal lineage of the developing zebrafish inner ear. When both sites are mutated, the loss of neurons and increase in cell death normally observed after six1a over-expression is abolished. Mutations in one site result in an intermediate condition. Values represent mean cell counts (± standard deviation) with a sample size of 20 embryos for each experiment. (A) Average number of hair cells and neurons in 3 dpf utricular maculae and SAG. Hair cells and neurons were detected by HCS-1 and HuC immunolabeling, respectively, using confocal microscopy. (B) Quantification of cell proliferation and death in otocysts at 28 hpf. Cells labeled with either PhosphoHistoneH3 or activated Caspase3. For cell proliferation and death, only cells within the otocyst were counted. Statistical analyses were performed for both panels with Student’s t test; all comparisons were made to embryos injected with standard MO control or with six1a mRNA. Comparisons where P < 0.05 were considered statistically significant.